[ubuntu] usb installation fails

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http://ubuntuforums.org – in a pc without cd/dvd drive i am trying to install ubuntu 12.04 LTS server edition 32bit from usb. by making use of the pendrive linux and the iso i have created a bootable usb drive. the system boots and after choosing the language and territory the installation fails due to a missing cdrom. i do not have lan connectivity at this point to start a netinstall. is there a way to install ubuntu server 12.04 server 32bit from usb? (Hardware)